In many applications it is desirable to interrupt the transmission of light, as in a system using fiber optic light transmission. Often such applications use an electrically controlled switch for moving a light blocking element into and out of a light beam transmission path, such switch requiring the applying of a voltage for generating a current to actuate the switch element. In many applications, however, where the switch may be used in a hazardous environment, the presence of electrical voltages and currents may be dangerous, since the possibility exists for the generation of an electrical spark or of generating excessive heat, e.g., where an electrical short circuit may arise, which might cause a fire or even an explosion in the hazardous environment.
It is desirable to design a switching device which requires no electrical voltage or current to be applied to the switching element. It is further helpful in many applications to provide a switching element which can be operated effectively in an environment in which vibrations are likely to occur.